1. Field of the Invention
This invention relates to semiconductor switches, and particularly to high-power switches.
2. Description of the Related Art
Semiconductor switches are increasingly required to control large amounts of power while conforming to demanding power loss requirements. Such switches are typically used in motor control systems, uninterrupted power supplies, high-voltage DC transmission, induction heating, and many other high power applications.
Typical high power switches include gate turn-off thyristors (GTO), insulated-gate bipolar transistors (IGBTs) and accumulation field effect transistors (FETs). (See The Electrical Engineering Handbook, Richard C. Dorf, CRC Press, 1997, pp 763–769). GTOs are current control devices that suffer from high power dissipation in the gate drive during turn-off because the reverse gate current amplitude is dependent on the anode current to be turned-off. For example, a 2000 A peak current GTO may require as high as 500 A of reverse gate current. In high frequency megawatt systems, such high reverse gate current losses are undesirable. Also, forward voltage drops across silicon based GTOs utilized in a 6.5 Kv system may approach 5 volts. An IGBT device in a similar system may experience a forward voltage drop approaching 7 or 8 volts. Accumulation FETs suffer from complex fabrication processes, thus limiting their use to lab scale demonstration rather than commercial scale applications.
A need continues to exist for a high power switch with a lower forward voltage drop, lower power dissipation and simple gate-drive circuitry, that does not require complex fabrication processes.